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Comment by wpollock | Hacker News Reader

Just because the cave is sealed now, does not mean it has been sealed for millions of years. Even for geology, 5.5M years is a long time. I don't understand how they can claim it never had connections to the outside, just because it doesn't have connections now.

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Geology is most probably largely how the sealed claim has been made .. it was open to the world when the limestone was forming, formed (Speleogenesis) by sky water (rain) permeating down and eating out a limestone void, and "sealed" by thick and impermeable layers of clays and loess (windborne sediment) some 2.5 million years ago during the Quaternary.

There are also genetic drift estimates, which put the "last" outside species to enter at about that time (

  One of the most recent animals recorded is the cave's only species of snail, Heleobia dobrogica, which has inhabited the cave for slightly more than 2 million years.

~ https://en.wikipedia.org/wiki/Movile_Cave )

Mentioning the recent Chernobyl accident is weird too. Surely an accident from long ago that is expected to be detectable is far more helpful.

All they proved is that nothing had entered since the Chernobyl accident.

Have there been many nuclear reactor meltdowns prior to Chernobyl?

Before 1986 there have been twelve "public" core meltdowns, and at least six, likely more, incidents not public on nuclear subs, etc.

~ https://en.wikipedia.org/wiki/Nuclear_and_radiation_accident...

You should look up how many live armed nuclear bombs have been accidentally dropped on mainland US soil.

More significantly, there's been a lot of above ground and atmospheric tests that have draped residuals across the planet, and a bunch of dirty Russian / former USSR sites that drift trace across Europe.

Isn't there a nuclear bomb sitting somewhere in a swamp in the USA that everybody lost?

"Yes"

- TBH I'd be surprised if it's still "lost" - not further reported on because [ XXXredactedXXX ] is more likely.

Also, if the finding is never recorded, it can be used to frame just about anyone who can be accused of finding it and smuggling it out of the US.

There have been natural nuclear reactors, but I don’t think any suffered a catastrophic event.

https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...

> Before 1986 there have been twelve "public" core meltdowns

Significantly before in relation to the 5.5 M year claim?

> You should look up how many live armed nuclear bombs have been accidentally dropped on mainland US soil.

Did they explode in a way that would lead to workers in Romania being able to detect their radioactivity in their cave?

You could just look for isotopes from the atmospheric nuclear tests that were conducted? Doesn't need to be a reactor I would assume?

Indeed. That's one of the reasons why the "Before Present" time scale (that uses 1/1/1950 as the epoch) is sometimes called "Before Physics" (another one being that 1950 is less and less "present", of course)!

> that uses 1/1/1950 as the epoch

I guess we can say this is when humankind reached adulthood, became able to drink and got a driver’s license. And a gun.

Yes.

But also, finding something from within the last hundred years doesn’t say an awful lot about something claimed to have been a closed system for millions of years.

It's an AI article.

Looking for Chernobyl signature in cave during the late 1980s / early 1990s does seem daft - far more likely for them to be looking for residual "trace" from the atmospheric tests that doused the planet in "unnatural" residuals and odd isotopes.

"Combined with the geology and the peculiar chemistry of the cave’s water and air, the evidence pointed to a system that had been closed off since roughly five and a half million years ago."

That quote, from the AI generated article, simply asserts the cave was sealed, it doesn't explain how the cave came to be sealed, nor how it is that modern humans infer the cave has been sealed and for how long.

On the flip side, the wiki article for the cave mentions that new species arrived as recently as 2 million years ago...

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